With the advent of artificial disc replacements and procedures such as posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF), there is an increasing need to retract posterior spinal bony structures such as the spinous processes. Most surgeons use a laminar spreader for this purpose, but the use of this instrument has its drawbacks.
A typical laminar spreader is shown in FIG. 1. The instrument 102 has a pair of handles 104, 106 coupled to arms 114, 116 through a joint 110, such that when the handles are compressed the arms spread apart. The handles may include knurled outer gripping surfaces such as 108. The tool further includes a mechanism 122 to bias a ratchet arm 124, which engages with tip 126 of handle 104 to hold the arms 114, 116 at a desired spread until released.
The arms 114, 116 terminate flattened tips with serrated edges 118, 120. The edges are placed between adjacent lamina to spread the lamina apart. The tool 102 is typically used after spinous processes have been removed with the lamina remaining. This instrument works well for the orientation of the laminar surface but in comparison, the spinous process contact area defines a very narrow vertical surface. As such, the tool just described can slide off or cut right through the spinous process contact area. Further, the spreading arms 114, 116 also obscure the surgeon's visualization, as the tool occupies too much space in and around the spinal midline for interspinous work.